Studies look at Don Pedro Reservoir’s benefits, impacts

Don Pedro Reservoir produces an estimated $4.8 billion in economic activity per year, a consultant said Thursday at a meeting on the federal relicensing of the system. The Modesto and Turlock irrigation districts are seeking a license that would replace the one that allowed completion of Don Pedro in 1971.

Don Pedro Reservoir produces an estimated $4.8 billion in economic activity per year, a consultant said Thursday at a meeting on the federal relicensing of the system. The meeting also dealt with salmon and steelhead trout in the Tuolumne River downstream of the dam – fish that could need more of the stored water if they are found to be in trouble.

The Modesto and Turlock irrigation districts are seeking a license that would replace the one that allowed completion of Don Pedro in 1971. The effort involves 38 studies, most of them on fish needs and some on economics and other topics.

The $4.8 billion is almost all from farming and food processing and includes products with a wide range of values, said economist Susan Burke of Cardno ENTRIX, a global consulting firm.

“But generally – you all know this – it’s high value,” she said. Farmland values in the district are 30 percent to 50 percent higher than in areas that rely on groundwater or the cutback-prone Central Valley Project, she added.

The economic activities include hydropower from Don Pedro and use of the reservoir for boating, fishing and other recreation.

The relicensing will cost an estimated $50 million. TID is paying about two-thirds of the cost, reflecting its share of the irrigation water, and MID is covering the rest.

Thursday’s meeting at MID headquarters came a month and a half after the districts filed their draft application with the Federal Energy Regulatory Commission. They are taking public comment in advance of filing a final application, expected April 30. FERC could grant a new license, including conditions for downstream fish and other concerns, in 2016.

Consultants have looked at how many salmon have returned from the Pacific Ocean to spawn each fall, and at what conditions they find in a river that has had reduced flows and other changes over more than a century.

The factors in salmon survival include the gravel where the eggs are laid, the floodplain where young fish spend part of their first year, and the volume and temperature of the water.

“Spawning habitat is the main bottleneck on the population,” said Noah Hume, an aquatic ecologist at Stillwater Sciences, based in Berkeley.

One study looked at how bald eagles have found winter habitat at Don Pedro. Others explored past human uses of the reservoir area. And experts had volunteers float in small boats past Modesto and other lower-river locales to see how much water would be needed to aid this kind of recreation.